Illinois weather in December
One place stands in for Illinois here — these are Chicago's numbers, not a statewide average.
Based on 1 weather station, in Chicago. One station — Chicago, where Lake Michigan runs the thermostat; downstate summers come hotter, and the far south of the state sees gentler winters.
Chicago & the Lakefront
Highs near 37°, nights around 24°, and 7.6 in of snow in a typical December.
| Place | Highs / lows | Wet days | Snow | The short version |
|---|---|---|---|---|
| Chicago | 37° / 24° | 6 | 7.6 in | Lights everywhere, and a lake that sharpens every block. |
Each place above has its own page for the full story — what the month feels like, what to pack, and whether the timing is right.